In one rare insight, Lee admitted in 1964 she had been completely caught off guard by being catapulted into the nation's consciousness by her novel.

"I hoped for a little, but I got rather a whole lot and in some ways this was just about as frightening as the quick, merciful death I'd expected," she said.

For decades after that she lived out of the public eye, claiming to have said all she wanted to say in "Mockingbird" and vowing never to publish another book.

But in 2015, she upended the literary world by publishing the unedited manuscript of "Go Set a Watchman" a first novel written in the 1950s and essentially the first draft of "Mockingbird."

The manuscript was an instant bestseller but its release sparked torrid speculation that she was not of sound mind and was mauled by critics who suggested she had tarnished her reputation.

Born Nelle Harper Lee in April 1926, she was the youngest of four children. Her father was also a lawyer and a direct descendant of Civil War general Robert E.Lee.

She counted author Truman Capote among her childhood friends, and worked as an assistant on his novel "In Cold Blood," which examined a multiple killing in Kansas, and was dedicated to Lee.

A precocious child, Lee learned to read early and had devoured all kinds of literature by the time she started school.

In a letter to talk show host Oprah Winfrey in May 2006, Lee told how growing up during the Great Depression of the 1930s in a remote village meant the few available books provided the only entertainment, turning reading into a lifelong passion.